The Discriminating Palate of Staphylococcus

Staphylococcus bacteria are heavy-hitting pathogens, causing illnesses such as food poisoning, meningitis, and toxic shock syndrome. But a new study identifies a stretch of DNA the bacteria need to get an essential nutrient, a breakthrough that the researchers hope will lead to drugs that stop the bugs cold.

Like all bacteria, Staphylococcus need iron to reproduce, and researchers hope to thwart the bugs by understanding how they scavenge this essential nutrient from their hosts. Suspecting that Staphylococcus might prefer a particular form of iron, microbiologists Eric Skaar and Olaf Schneewind of the University of Chicago offered Staphylococcus aureus a choice of two isotope-labeled compounds. By detecting the isotope labels after the bacteria chowed down, the team learned that the bacteria prefer to steal iron from heme, the iron-containing part of hemoglobin, rather than from an iron-ferrying protein called transferrin. Heme iron makes up 80% of the body's total iron.

Skaar and Schneewind then analyzed the S. aureus genome and identified the span of genetic code responsible for the bacteria's uptake of heme iron. Then they deactivated this stretch of DNA before injecting S. aureus into worms and mice. Whereas normal S. aureus killed the worms and caused abscesses on the organs of mice, the treated bacteria caused much milder infections--killing very few worms and causing no abscesses in the mice. This is encouraging, the authors write in the 10 September issue of Science. Understanding how Staphylococcus bacteria use iron could lead to drugs that block heme-iron uptake and minimize the severity of infections.

The research is a “significant” contribution to understanding how iron uptake moderates the spread of bacterial infection, says microbiologist Shelley Payne of the University of Texas, Austin.